Recently, it has been demanded that an information storage medium has an improved storage capacity so as to allow processing of information of large quantity, such as an image or the like.
One way of improving the storage capacity of the information storage medium may be to multi-layer the information storage medium so as to have a plurality of information storage layers. For example, an information storage medium having up to two information storage layers are currently standardized and commercially available in form of DVD (Digital Versatile. Disc), BD (Blu-ray Disc; Registered Trademark), or the like.
An information storage medium having two or more information storage layers has a drawback described as follows. Some of the information storage layers are away from a side on which reproducing light enters the information storage medium. For reproduction of image from such information storage layer, the reproducing light having entered the information storage medium has to be transmitted through others of the information storage layer which are close to the side. In order for the reproducing light to be transmitted, however, reflectances of the information storage layers close to the side have to be small. Further, as the information storage medium is multi-layered to have the plurality of information storage layers, there is an adverse effect that light reflected from the information storage layer away from the side is decreased in intensity.
Due to such a problem, it is particularly difficult to provide a plurality of rewritable information storage layers in a single optical disc. Currently, not more than two (2) information storage layers can be provided in the single optical disc.
Meanwhile, an optical information storage medium described as follows has been recently demanded. Specifically, the demanded type of the optical information storage medium has an improved storage capacity by having a rewritable information storage layer and a read-only or recordable information storage layer in which various contents are recorded (hereinafter, the demanded type of the optical information storage medium is sometimes referred to as a “hybrid optical information storage medium”).
The rewritable information storage layer, the read-only information storage layer, and the recordable information storage layer are hereinafter referred to as an RE (RE-writable) layer, an ROM (Read Only Memory) layer, and an R (Recordable) layer, respectively.
As one technique related to such multi-layered information storage medium, Patent Literature 1 discloses an optical disc and an optical disc apparatus disclosed.
The optical disc of Patent Literature 1 is a single optical disc having a plurality of information storage layers complying with respective different optical disc specifications. In the optical disc of Patent Literature 1, pieces of information indicative types of the respective plurality of information storage layers are stored in a management region of that of the plurality of information storage layers which has a storage density greater than the rest of the plurality of information storage layers.
The optical disc apparatus of Patent Literature 1 reads out the pieces of information by accessing this management region of the information storage section and holds them. Then, the optical disc apparatus of Patent Literature 1 determines which of the plurality of information storage layer to access. Based on the pieces of information indicative of the types of the respective plurality of information storage layers, the, optical disc apparatus of Patent Literature 1 sets a recording and reproduction scheme or the like (such as power setting) as suitable for the information storage layer to access.
Citation List
Patent Literature 1
Japanese Patent Application Publication, Tokukai, No. 2006-260610 A (Publication Date: Sep. 28, 2006)